Semiconductor device and manufacturing method thereof

ABSTRACT

A semiconductor device includes a fin structure disposed over a substrate, a gate structure and a source. The fin structure includes an upper layer being exposed from an isolation insulating layer. The gate structure disposed over part of the upper layer of the fin structure. The source includes the upper layer of the fin structure not covered by the gate structure. The upper layer of the fin structure of the source is covered by a crystal semiconductor layer. The crystal semiconductor layer is covered by a silicide layer formed by Si and a first metal element. The silicide layer is covered by a first metal layer. A second metal layer made of the first metal element is disposed between the first metal layer and the isolation insulating layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional Application of U.S. Ser. No. 16/370,521filed Mar. 29, 2019, now U.S. Pat. No. 10,714,349, which is a DivisionalApplication of U.S. Ser. No. 15/836,448 filed Dec. 8, 2017, now U.S.Pat. No. 10,269,572, which is a Divisional Application of U.S. Ser. No.15/485,340 filed Apr. 12, 2017, now U.S. Pat. No. 9,875,902, which is aDivisional Application of U.S. Ser. No. 15/058,672 filed Mar. 2, 2016,now U.S. Pat. No. 9,653,604, which claims priority to U.S. ProvisionalPatent Application 62/273,361 filed Dec. 30, 2015. The subject matter ofeach is incorporated herein by reference in entirety.

TECHNICAL FIELD

The disclosure relates to a semiconductor integrated circuit, moreparticularly to a source/drain structure for a fin field effecttransistor (FinFET) and its manufacturing process.

BACKGROUND

As the semiconductor industry has progressed into nanometer technologyprocess nodes in pursuit of higher device density, higher performance,and lower costs, challenges from both fabrication and design issues haveresulted in the use of a metal gate structure with a high-k (dielectricconstant) material. The metal gate structure is often manufactured byusing gate replacement technologies, and source and drain are formed ina recessed fin by using an epitaxial growth method. One of thechallenges, however, in the present technologies is reducing currentcrowding at the source and drain and increasing the transistor's currentdrive ability.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIGS. 1-11 show exemplary views of various stages of a sequentialmanufacturing operation for a semiconductor FET device according to afirst embodiment of the present disclosure.

FIGS. 12-14 show exemplary views of various stages of a sequentialmanufacturing operation for a semiconductor FET device according to asecond embodiment of the present disclosure.

FIGS. 15 and 16 show exemplary views of various stages of a sequentialmanufacturing operation for a semiconductor FET device according to athird embodiment of the present disclosure.

FIGS. 17A-17H show exemplary views of various stages of a sequentialmanufacturing operation for a semiconductor FET device according to afourth embodiment of the present disclosure.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof the invention. Specific embodiments or examples of components andarrangements are described below to simplify the present disclosure.These are, of course, merely examples and are not intended to belimiting. For example, dimensions of elements are not limited to thedisclosed range or values, but may depend upon process conditions and/ordesired properties of the device. Moreover, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed interposing the first and second features, suchthat the first and second features may not be in direct contact. Variousfeatures may be arbitrarily drawn in different scales for simplicity andclarity.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. In addition, the term“made of” may mean either “comprising” or “consisting of.”

FIGS. 1-11 show exemplary views of various stages of a sequentialmanufacturing operation of a source/drain structure for a semiconductorFET device according to a first embodiment of the present disclosure. Itis understood that additional operations may be provided before, during,and after processes shown by FIG. 1, and some of the operationsdescribed below can be replaced or eliminated for additional embodimentsof the method. The order of the operations/processes may beinterchangeable. In this disclosure, a source and a drain areinterchangeably used and “source/drain” refers to one of or both of asource and a drain of an FET.

The following embodiments mainly describe a FinFET device as one exampleof the semiconductor device and the manufacturing method thereof, andthe technologies described herein are also applicable to horizontalgate-all-around (GAA) type transistors or channel-on-oxide typetransistors.

FIG. 1 is an exemplary perspective view of one stage of the sequentialmanufacturing process of the semiconductor device according to the firstembodiment of the present disclosure.

FIG. 1 shows a structure after fin structures are formed. One or morefin structures 20 are formed over a substrate 10, and protrude from anisolation insulating layer 50. In one embodiment, each of the finstructures 20 includes a well layer 20B and a channel layer 20A. In thepresent embodiment, the fin structures 20 include silicon. In otherembodiments, the fin structures 20 include Si_(1-x)Ge_(x), where x is0.1 to 0.9. Hereinafter, Si_(1-x)Ge_(x) may be simply referred to asSiGe.

To fabricate fin structures, a mask layer is formed over a substrate,for example, a Si substrate 10. The mask layer is formed by, forexample, a thermal oxidation process and/or a chemical vapor deposition(CVD) process. The substrate 10 is, for example, a p-type siliconsubstrate with an impurity concentration in a range from about 1×10¹⁵ cm⁻³ to about 1×10¹⁸ cm⁻³. In other embodiments, the substrate 10 is ann-type silicon substrate with an impurity concentration in a range fromabout 1×10¹⁵ cm⁻³ to about 1×10¹⁸ cm³. The mask layer includes, forexample, a pad oxide (e.g., silicon oxide) layer and a silicon nitridemask layer.

Alternatively, the substrate 10 may comprise another elementarysemiconductor, such as germanium; a compound semiconductor includingIV-IV compound semiconductors such as SiC and SiGe, III-V compoundsemiconductors such as GaAs, GaP, GaN, InP, InAs, InSb, GaAsP, AlGaN,AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; or combinations thereof.In one embodiment, the substrate 10 is a silicon layer of an SOI(silicon-on insulator) substrate. When an SOI substrate is used, the finstructure may protrude from the silicon layer of the SOI substrate ormay protrude from the insulator layer of the SOI substrate. In thelatter case, the silicon layer of the SOI substrate is used to form thefin structure. Amorphous substrates, such as amorphous Si or amorphousSiC, or insulating material, such as silicon oxide may also be used asthe substrate 10. The substrate 10 may include various regions that havebeen suitably doped with impurities (e.g., p-type or n-typeconductivity).

The pad oxide layer may be formed by using thermal oxidation or a CVDprocess. The silicon nitride mask layer may be formed by a physicalvapor deposition (PVD), such as a sputtering method, a CVD,plasma-enhanced chemical vapor deposition (PECVD), an atmosphericpressure chemical vapor deposition (APCVD), a low-pressure CVD (LPCVD),a high density plasma CVD (HDPCVD), an atomic layer deposition (ALD)and/or other processes.

The thickness of the pad oxide layer is in a range from about 2 nm toabout 15 nm and the thickness of the silicon nitride mask layer is in arange from about 2 nm to about 50 nm in some embodiments. A mask patternis further formed over the mask layer. The mask pattern is, for example,a resist pattern formed by lithography operations.

By using the mask pattern as an etching mask, a hard mask pattern of thepad oxide layer and the silicon nitride mask layer is formed. The widthof the hard mask pattern is in a range from about 5 nm to about 40 nm insome embodiments. In certain embodiments, the width of the hard maskpatterns is in a range from about 4 nm to about 12 nm.

By using the hard mask pattern as an etching mask, the Si substrate ispatterned into fin structures 20 by trench etching using a dry etchingmethod and/or a wet etching method.

The width of the fin structure 20 is in a range from about 5 nm to about40 nm in some embodiments, and is in a range from about 4 nm to about 12nm in certain embodiments. The height of the fin structure 20 is in arange from about 100 nm to about 300 nm in some embodiments, and is in arange from about 50 nm to about 100 nm in other embodiments. When theheights of the fin structures are not uniform, the height from thesubstrate may be measured from the plane that corresponds to the averageheights of the fin structures. The height of the channel layer 20A is ina range from about 35 nm to about 80 nm in some embodiments. The spacebetween the fin structures 20 is in a range from about 5 nm to about 80nm in some embodiments, and is in a range from about 7 nm to about 20 nmin other embodiments. One skilled in the art will realize, however, thatthe dimensions and values recited throughout the descriptions are merelyexamples, and may be changed to suit different scales of integratedcircuits.

In FIG. 1, three fin structures 20 extending in the X direction aredisposed adjacent to each other in the Y direction. However, the numberof the fin structures is not limited to three. The numbers may be one,two, four or five or more. In addition, one of more dummy fin structuresmay be disposed adjacent to both sides of the fin structures 20 toimprove pattern fidelity in patterning processes.

After forming the fin structures 20, an isolation insulating layer 50 isformed over the fin structures 20. The isolation insulating layer 50includes one or more layers of insulating materials, for example,silicon dioxide, silicon oxynitride and/or silicon nitride formed byLPCVD (low pressure chemical vapor deposition), plasma-CVD or spin-ondeposition of a flowable insulator. In the flowable depositiontechnique, flowable dielectric materials instead of silicon oxide aredeposited. Flowable dielectric materials, as their name suggest, can“flow” during deposition to fill gaps or spaces with a high aspectratio. Usually, various chemistries are added to silicon-containingprecursors to allow the deposited film to flow. In some embodiments,nitrogen hydride bonds are added. Examples of flowable dielectricprecursors, particularly flowable silicon oxide precursors, include asilicate, a siloxane, a methyl silsesquioxane (MSQ), a hydrogensilsesquioxane (HSQ), an MSQ/HSQ, a perhydrosilazane (TCPS), aperhydro-polysilazane (PSZ), a tetraethyl orthosilicate (TEOS), or asilyl-amine, such as trisilylamine (TSA). These flowable silicon oxidematerials are formed in a multiple-operation process. After the flowablefilm is deposited, it is cured and then annealed to remove un-desiredelement(s) to form silicon oxide. When the un-desired element(s) isremoved, the flowable film densifies and shrinks. In some embodiments,multiple anneal processes are conducted. The flowable film is cured andannealed more than once. The flowable film may be doped with boronand/or phosphorous. The isolation insulating layer 50 may be formed byone or more layers of SOG, SiO, SiON, SiOCN or fluorine-doped silicateglass (FSG) in some embodiments.

After forming the isolation insulating layer 50 over the fin structures20, a planarization operation is performed so as to remove part of theisolation insulating layer 50 and the mask layer (the pad oxide layerand the silicon nitride mask layer). The planarization operation mayinclude a chemical mechanical polishing (CMP) and/or an etch-backprocess. Then, the isolation insulating layer 50 is further removed sothat the channel layer 20A of the fin structure 20 is exposed, as shownin FIG. 1.

In certain embodiments, the partially removing the isolation insulatinglayer 50 may be performed using a wet etching process, for example, bydipping the substrate in hydrofluoric acid (HF). In another embodiment,the partially removing the isolation insulating layer 50 may beperformed using a dry etching process. For example, a dry etchingprocess using CHF₃ or BF₃ as etching gases may be used.

After forming the isolation insulating layer 50, a thermal process, forexample, an anneal process, may be performed to improve the quality ofthe isolation insulating layer 50. In certain embodiments, the thermalprocess is performed by using rapid thermal annealing (RTA) at atemperature in a range from about 900° C. to about 1050° C. for about1.5 seconds to about 10 seconds in an inert gas ambient, such as an N₂,Ar or O₂ ambient.

In the present embodiment, a gate replacement technology is employed. Asshown in FIG. 2, a dummy gate structure 40 is formed over part of thefin structures 20. FIG. 2 is an exemplary perspective view of the FinFETdevice at one stage of the sequential fabrication process according tothe first embodiment. FIG. 3A is an exemplary cross sectional view alongthe line a-a of FIG. 2 (a gate region), and FIG. 3B is an exemplarycross sectional view along the line b-b of FIG. 2 (a source/drainregion). FIGS. 4-11 show exemplary cross sectional view corresponding tothe line b-b of FIG. 2.

A dielectric layer and a polysilicon layer are formed over the isolationinsulating layer 50 and the exposed fin structures 20A, and thenpatterning operations are performed so as to obtain a dummy gatestructure 40 including a dummy gate electrode layer 45 made ofpolysilicon and a dummy gate dielectric layer 30. The patterning of thepolysilicon layer is performed by using a hard mask 60 including asilicon nitride layer 64 formed over an oxide layer 62 in someembodiments. In other embodiments, the hard mask may include a siliconoxide layer formed over a nitride layer. The dummy gate dielectric layer30 may be silicon oxide formed by CVD, PVD, ALD, e-beam evaporation, orother suitable process. In some embodiments, the gate dielectric layer30 may include one or more layers of silicon oxide, silicon nitride,silicon oxy-nitride, or high-k dielectrics. In some embodiments, athickness of the gate dielectric layer is in a range from about 5 nm toabout 20 nm, and in a range from about 5 nm to about 10 nm in otherembodiments.

The gate electrode layer 45 may comprise a single layer or multilayerstructure. The dummy gate electrode layer 45 may be doped polysiliconwith uniform or non-uniform doping. The dummy gate electrode layer 45may be formed using a suitable process such as ALD, CVD, PVD, plating,or combinations thereof. In the present embodiment, the width of thedummy gate electrode layer 45 is in the range of about 30 nm to about 60nm. In some embodiments, a thickness of the gate electrode layer is in arange from about 30 nm to about 50 nm.

The dummy gate structure 40 may include side-wall insulating layers 47disposed over both main sides of the dummy gate electrode 45. Theside-wall insulating layers 47 include one or more layers of siliconoxide, silicon nitride, silicon oxy-nitride, or other suitable material.The side-wall insulating layers 47 may comprise a single layer ormultilayer structure. A blanket layer of a side-wall insulating materialmay be formed by CVD, PVD, ALD, or other suitable technique. Then, ananisotropic etching is performed on the side-wall insulating material toform a pair of side-wall insulating layers (spacers) 47 on two mainsides of the gate structure. The thickness of the side-wall insulatinglayers 47 is in a range from about 1 nm to about 20 nm in someembodiments, and in a range from about 2 nm to about 10 nm in otherembodiments.

As shown in FIG. 4, spacer layers 100 are formed on sidewalls of the finstructures 20 in the source/drain (S/D) region. The spacer layers 100include one or more layers of silicon oxide, silicon nitride, siliconoxy-nitride, or other suitable material. In this embodiment, a siliconnitride based material, such as SiN or SiCN is used. A blanket layer ofan insulating material for the spacer layer is formed by CVD, PVD, ALD,or other suitable technique over the structure of FIG. 2. Then, ananisotropic etching is performed on the blanket layer to form a pair ofspacer layers 100 on two main sidewalls of the fin structure and toleave a space 105 between the spacer layers. The width of the space 105is in a range from about 4 nm to about 30 nm in some embodiments. Thethickness of the spacer layers 100 is in a range from about 1 nm toabout 10 nm in some embodiments, and in a range from about 2 nm to about5 nm in other embodiments. In some embodiments, the spacer layers 100are formed by the operations to form the side-wall insulating layers 47for the dummy gate structure.

Subsequently, as shown in FIG. 5, first metal layers 110 are formed inthe space 105 of the structure of FIG. 4. A blanket layer of the firstmetal material is formed over the structure of FIG. 4, and aplanarization operation, such as an etch-back process, is performed sothat the first metal material is filled in the space 105. The firstmetal layer 110 includes one or more of Co, Ti, Ta, W or Ni, or othersuitable metal materials. The first metal layer is formed by CVD, PVD,ALD, or other suitable techniques.

After the first metal layers 110 are formed, the spacer layers 100 areremoved, by using a wet etching, thereby leaving spaces 115, as shown inFIG. 6.

Next, as shown in FIG. 7, an amorphous layer 120 is formed over thestructure shown in FIG. 6. The amorphous layer 120 is formed so as tofully fill the spaces 115 to be higher than the fin structures 20.

The amorphous layer 120 may be made of the same material as the finstructures 20 or a different material. When the fin structure 20 is madeof Si and the FinFET is an n-type, the amorphous layer 120 may be madeof Si or SiP. When the fin structure 20 is made of Si and the FinFET isa p-type, the amorphous layer 120 is made of Si, SiGe or SiGeB. When thefin structure 20 is made of SiGe and the FinFET is an n-type, theamorphous layer 120 may be made of Si or SiGe, and when the finstructure 20 is made of SiGe and the FinFET is a p-type, the amorphouslayer 120 is made of Ge or SiGe.

The amorphous layer 120 is heavily doped with an appropriate dopant atan amount of about 2×10²⁰ cm⁻³ to about 1×10²¹ cm ³. The dopant for ap-type FET includes boron, and the dopant for an n-type FET includesphosphorous and/or arsenic.

The amorphous layer 120 may be formed by a CVD method using SiH₄,SiHCl₃, SiH₂Cl₂ and/or Si₂H₆ as a source gas for amorphous silicon, orGeH₄ for amorphous SiGe. An ALD method may also be used. The amorphouslayer 120 is produced by the pyrolysis (thermal decomposition of one ofthe abovementioned gases) at a temperature between, for example, about520 and about 620 degrees Celsius and in the pressure range of about 2to about 300 mTorr.

Subsequently, part of the amorphous layer 120 in contact with the finstructures 20 is recrystallized by a thermal operation, as shown in FIG.8. This recrystallization is often called as solid-phase epitaxy.

In the recrystallization operations, the substrate with the dummy gatestructure 40 and the fin structure 20 covered by the amorphous layer 120is heated at a temperature of about 450° C. to about 650° C. in someembodiments, or at a temperature of about 550° C. to 600° C. in otherembodiments, when the amorphous layer 120 is amorphous silicon. By thissolid-phase epitaxy, a few nanometer layer of the amorphous layer 120 isrecrystallized into recrystallized layer 130, by using the fin structure20 (crystal silicon) as a seed layer. The thickness of therecrystallized layer 130 is in a range from about 0.5 nm to about 4 nm.The amorphous layer 120 formed on insulating layers is notrecrystallized.

When the amorphous layer 120 is amorphous SiGe, the heating temperatureis in a range from about 400° C. to 550° C. in some embodiments.

As shown in FIG. 9, the recrystallized layer 130 grows substantiallyuniformly on the top and the side faces of the exposed fin structure 20.The difference of the thickness of the grown recrystallized layer 120between the side face and the top face may be about 0.2 nm to about 1nm. If a vapor phase epitaxy is used instead of solid-phase epitaxy asdescribed above, an epitaxially grown layer would grow more laterallythan vertically due to different growth rates for crystal orientationsof Si, thereby forming a “diamond” shape cross section.

After the recrystallization operation, the remaining amorphous layers120 that are not recrystallized are removed by, for example, wet etchingoperations. In case of wet etching, dilute HNO₃ and HF is used as anetching solution. A tetramethylammonium hydroxide (TMAH) solution,ammonia (NH₄OH) or a potassium hydroxide (KOH) solution or a CF₄O₂plasma may also be used. Dry etching may be used to remove thenon-crystallized amorphous layer.

After the remaining, non-used amorphous layers 120 are removed, a secondmetal layer 140 is formed over the structure of FIG. 9, as shown in FIG.10. The metal material for the second metal layer 140 is the same as thefirst metal layer 110 in this embodiment. In other embodiments, adifferent metal material is used.

Subsequently, as shown in FIG. 11, silicide layers 150 are formedbetween the recrystallized layer 130 and the first and second metallayers 110, 140.

To form the silicide layer 150, a thermal operation, such as a rapidthermal annealing (RTA) operation, is performed. The substrate 10 isheated at about 900° C. to about 1100° C. when the first and secondmetal layers are made of W, at about 600° C. to about 800° C. when thefirst and second metal layers are made of Co, at about 700° C. to about900° C. when the first and second metal layers are made of Ti, or atabout 400° C. to about 600° C., when the first and second metal layersare made of Ni.

As shown in FIG. 11, a part of the recrystallized layer 130 becomes thesilicide layers 150. The thickness of the silicide layer 150 is in arange from 1 nm to 5 nm in some embodiments. When the recrystallizedlayer 130 is thin, the entire recrystallized layer 130 becomes thesilicide layers 150, and further part of the fin structure 20 alsobecomes the silicide layers 150. In such cases, the thickness of thesilicide layers 150 is in a range from about 5 nm to about 15 nm in someembodiments.

As shown in FIG. 11, since the recrystallized layers 130 aresubstantially uniformly grown over the exposed fin structure 20, thesilicide layers 150 are also substantially uniformly formed. Thedifference of the thickness of the silicide layer 150 between the sideface and the top face of the fin structure 20 is about 0.2 nm to about 1nm in some embodiments.

After the silicide layers 150 are formed, a dielectric layer is formed,and then the dummy gate electrode layer 45 and the dummy dielectriclayer 30 are removed, by appropriate etching processes, respectively, toform an opening. A metal gate structure is formed in the opening createdby removing the dummy gate structure. A gate dielectric layer and ametal gate layer are formed in the opening. A gate dielectric layer isformed over an interface layer disposed over the channel layer of thefin structure. The interface layer may include silicon oxide with athickness of 0.2 nm to 1.5 nm in some embodiments. The silicon oxideinterface layer may be formed by oxidizing the Si channel layer. Inother embodiments, the thickness of the interface layer is in a rangeabout 0.5 nm to about 1.0 nm. The gate dielectric layer includes one ormore layers of a dielectric material, such as silicon oxide, siliconnitride, or high-k dielectric material, other suitable dielectricmaterial, and/or combinations thereof. Examples of high-k dielectricmaterial include HfO₂, HfSiO, HfSiON, HfTaO, HfTiO, HfZrO, zirconiumoxide, aluminum oxide, titanium oxide, hafnium dioxide-alumina(Hfo₂-Al₂O₃) alloy, other suitable high-k dielectric materials, and/orcombinations thereof. The gate dielectric layer 75 is formed by, forexample, chemical vapor deposition (CVD), physical vapor deposition(PVD), atomic layer deposition (ALD), high density plasma CVD (HDPCVD),or other suitable methods, and/or combinations thereof. A metal gateelectrode is formed over the gate dielectric layer. The metal gateelectrode include one or more layers of any suitable metal material,such as aluminum, copper, titanium, tantalum, cobalt, molybdenum,tantalum nitride, nickel silicide, cobalt silicide, TiN, WN, TiAl,TiAlN, TaCN, TaC, TaSiN, metal alloys, other suitable materials, and/orcombinations thereof. In certain embodiments of the present disclosure,one or more work function adjustment layers may be interposed betweenthe gate dielectric layer and the gate electrode. The work functionadjustment layers are made of a conductive material such as a singlelayer of TiN, TaN, TaAlC, TiC, TaC, Co, Al, TiAl, HfTi, TiSi, TaSi orTiAlC, or a multilayer of two or more of these materials. For the p-typeFinFET, one or more of TiAlC, Al, TiAl, TaN, TaAlC, TiN, TiC and Co maybe used as the work function adjustment layer.

In the above fabrication process, when the S/D structures for n-typeFinFETs are fabricated, the regains where p-type FETs are formed arecovered by a protective layer, such as SiN. Similarly, when the S/Dstructures for p-type FinFETs are fabricated, the regions where then-type FETs are formed are covered by a protective layer.

It is understood that further CMOS processes are performed to formvarious features such as contacts/vias, interconnect metal layers,dielectric layers, passivation layers, etc.

In the present embodiment, since the first metal layer is formed beforethe recrystallization of the amorphous layer, it is possible to increasepacking density (to reduce fin pitch/space) in the source/drainstructure. Further, by using a solid phase epitaxy, a recrystallizedlayer substantially uniformly grows on the top and the side faces of theexposed fin structure. The recrystallized layer fully covers the exposedfin structure, the silicide layer also fully covers the recrystallizedlayer, and therefore the S/D contact plug can cover the entiresource/drain regions of the fin structure. Accordingly, the contactresistance between the S/D metal electrode layers and the source/drainregions can be reduced.

FIGS. 12-14 show exemplary views of various stages of a sequentialmanufacturing operation for a semiconductor FET device according to asecond embodiment of the present disclosure. The configurations,materials and/or processes as described with the first embodiment may beapplied to the second embodiment, and the details thereof may beomitted.

In the second embodiment, more than one metal material is used to fillthe space 105. After the structure of FIG. 4 is formed, a thin thirdmetal layer 112 is formed and then the first metal layer 110 is formed,followed by the planarization operation, thereby obtaining the structureshown in FIG. 12. The metal material for the third metal layer 112 isdifferent from the metal material for the first metal layer. The thirdmetal layer 112 includes one or more of Co, Ti, W or Ni, or othersuitable metal materials. The third metal layer is formed by CVD, PVD,ALD, or other suitable techniques. The third metal layer 112 is a metalhaving a lower silicide formation temperature and forming a higherquality of silicide than the first metal layer 110. When the first metallayer 110 is W, the third metal layer 112 is Ni and/or Ti for an n-typeFET, and Ni, Ti and/or Ta for a p-type FET. The thickness of the thirdmetal layer 112 is smaller than the thickness of the first metal layerand is in a range from about 0.5 nm to about 3 nm in some embodiments.

After the planarization operation on the first and third metal layer,the fabrication operations descried with FIGS. 6-9 are performed.

Then, as shown in FIG. 13, a fourth metal layer 142 is formed and thesecond metal layer 140 is further formed on the fourth metal layer 142.The fourth metal layer 142 is a metal having a lower silicide formationtemperature and forming a higher quality of silicide than the firstand/or second metal layers. The second metal layer 140 is a materialhaving a lower resistivity than the third and/or fourth metal layers.The metal material for the second metal layer 140 is the same as thefirst metal layer 110 and the metal material for the third metal layer112 is the same as the fourth metal layer 142 in this embodiment. Inother embodiments, different metal materials are used. The thickness ofthe fourth metal layer 142 is in a range from about 0.5 nm to about 3 nmin some embodiments.

Subsequently, as shown in FIG. 14, silicide layers 152 are formedbetween the recrystallized layer 130 and the third and fourth metallayers 112, 142, by the similar thermal operation described with FIG.11.

In the second embodiment, by using a metal material having a lowersilicide formation temperature and forming a higher quality of silicideas a silicide source (e.g., third and fourth metal layers) and using ametal material having a lower resistivity as the contact metal layercovering the silicide layer (e.g., first and second metal layers), it ispossible to reduce the overall process temperature and thermal budget,while achieving a good electrical conductivity at the soured/drain. Inparticular, the contact resistance to the S/D contact plug can belowered.

FIGS. 15-16 show exemplary views of various stages of a sequentialmanufacturing operation for a semiconductor FET device according to athird embodiment of the present disclosure. The configurations,materials and/or processes as described with the first and secondembodiments may be applied to the third embodiment, and the detailsthereof may be omitted.

Similar to the second embodiment, two metal layers 110 and 112 areformed as shown in FIG. 12. After the planarization operation on thefirst and third metal layer, the fabrication operations descried withFIGS. 6-9 are performed.

Then, as shown in FIG. 15, the second metal layer 140 is formed, withoutforming a fourth metal layer. The second metal layer 140 is a materialhaving a lower resistivity than the third metal layer 112. The metalmaterial for the second metal layer 140 is the same as the first metallayer 110 in this embodiment. In other embodiments, a different metalmaterial is used.

Subsequently, as shown in FIG. 16, a lower silicide layer 154 is formedbetween the recrystallized layer 130 and the third metal layer 112 andan upper silicide layer 156 is formed between the recrystallized layer130 and the second metal layer 140, by the similar thermal operationdescribed with FIG. 11.

In the third embodiment, the similar advantages to the second embodimentcan be obtained. In the third embodiment, the contact resistance to theS/D contact plug can be further lowered than the second embodiment.Although the quality of the upper silicide layer 156 may be lower thanthe quality of the lower silicide layer 154, the area/volume of theupper silicide layer 156 is much smaller than the lower silicide layer154, and therefore the effect of the upper silicide layer 156 on theelectrical properties of the S/D structure is limited.

FIGS. 17A-17H show exemplary views of various stages of a sequentialmanufacturing operation for a semiconductor FET device according to afourth embodiment of the present disclosure. In the fourth embodiment,an S/D structure for one fin structure is fabricated. Theconfigurations, materials and/or processes as described with the firstto third embodiments may be applied to the fourth embodiment, and thedetails thereof may be omitted.

In FIG. 17A, similar to FIG. 4, spacer layers 25 are formed on sidewallsof the fin structure 20 in the source/drain (S/D) region.

In FIG. 17B, similar to FIG. 5, first metal layers 65 are formed on thesidewalls of the spacer layers 25.

In FIG. 17C, similar to FIG. 6, the spacer layer 25 are removed.

In FIG. 17D, similar to FIG. 7, an amorphous layer 70 is formed.

In FIG. 17E, similar to FIG. 8, portions of the amorphous layer 70 incontact with the fin structure 20 are recrystallized to form arecrystallized layer 75.

As shown in FIG. 17F, similar to FIG. 9, the remaining, unused amorphouslayer 70 is removed.

As shown in FIG. 17G, similar to FIG. 10, a second metal layer 80 isformed.

As shown in FIG. 17H, similar to FIG. 11, by the thermal operation, asilicide layer 90 is formed. The second metal layer 80 formed on thesurface of the isolation insulating layer 50 is be removed byappropriate etching operations, including wet and/or dry etching.

It will be understood that not all advantages have been necessarilydiscussed herein, no particular advantage is required for allembodiments or examples, and other embodiments or examples may offerdifferent advantages.

In accordance with one aspect of the present disclosure, in a method ofmanufacturing a semiconductor device including a FinFET, a first finstructure and a second fin structure are formed over a substrate. Thefirst and second fin structures extend in a first direction and protrudefrom an isolation insulating layer. A gate structure is formed over partof the first and second fin structures. The gate structure extends in asecond direction perpendicular to the first direction. Sidewall spacersare formed on both major side surfaces of each of the first and secondfin structures not covered by the gate structure. First metal layers areformed on the sidewall spacers, thereby filling a space between thefirst and second fin structures. After forming the first metal layers,the sidewall spacers are removed. After removing the sidewall spacers,an amorphous layer in contact with the fin structure is formed. Arecrystallized layer is formed by partially recrystallizing theamorphous layer on the fin structure. A remaining amorphous layer whichis not recrystallized is removed. After removing the remaining amorphouslayer, a second metal layer is formed. Silicide layers are formed by asilicide reaction between the recrystallized layer and the first metallayers and the second metal layer.

In accordance with another aspect of the present disclosure, in a methodof manufacturing a semiconductor device including a FinFET, a first finstructure and a second fin structure are formed over a substrate. Thefirst and second fin structures extend in a first direction and protrudefrom an isolation insulating layer. A gate structure is formed over partof the first and second fin structures. The gate structure extends in asecond direction perpendicular to the first direction. Sidewall spacersare formed on both major side surfaces of each of the first and secondfin structures not covered by the gate structure. First metal layers areformed on the sidewall spacers and second metal layers on the firstmetal layers, thereby filling a space between the first and second finstructures. After forming the first and second metal layers, thesidewall spacers are removed. After removing the sidewall spacers, anamorphous layer in contact with the fin structure is formed. Arecrystallized layer is formed by partially recrystallizing theamorphous layer on the fin structure. A remaining amorphous layer whichis not recrystallized is removed. After removing the remaining amorphouslayer, a third metal layer is formed. Silicide layers, formed by asilicide reaction between the recrystallized layer and the first metallayers and the third metal layer, are formed.

In accordance with another aspect of the present disclosure, asemiconductor device includes a fin structure disposed over a substrate,a gate structure and a source. The fin structure includes an upper layerbeing exposed from an isolation insulating layer. The gate structuredisposed over part of the upper layer of the fin structure. The sourceincludes the upper layer of the fin structure not covered by the gatestructure. The upper layer of the fin structure of the source is coveredby a crystal semiconductor layer. The crystal semiconductor layer iscovered by a silicide layer formed by Si and a first metal element. Thesilicide layer is covered by a first metal layer. A second metal layermade of the first metal element is disposed between the first metallayer and the isolation insulating layer.

The foregoing outlines features of several embodiments or examples sothat those skilled in the art may better understand the aspects of thepresent disclosure. Those skilled in the art should appreciate that theymay readily use the present disclosure as a basis for designing ormodifying other processes and structures for carrying out the samepurposes and/or achieving the same advantages of the embodiments orexamples introduced herein. Those skilled in the art should also realizethat such equivalent constructions do not depart from the spirit andscope of the present disclosure, and that they may make various changes,substitutions, and alterations herein without departing from the spiritand scope of the present disclosure.

What is claimed is:
 1. A semiconductor device comprising: a fin structure disposed over a substrate, the fin structure including an upper layer being exposed from an isolation insulating layer; a gate structure disposed over part of the upper layer of the fin structure; and a source which includes the upper layer of the fin structure not covered by the gate structure, wherein: the upper layer of the fin structure of the source is covered by a crystal semiconductor layer, the crystal semiconductor layer is covered by a first silicide layer formed by Si and a first metal element and a second silicide layer formed by Si and a second metal element different from the first metal element, and the second silicide layer covers a different portion of the crystal semiconductor layer than the first silicide layer.
 2. The semiconductor device of claim 1, wherein the first and second silicide layers are covered by a first metal layer containing the second metal element.
 3. The semiconductor device of claim 2, further comprising a second metal layer made of the first metal element disposed between the first metal layer and the isolation insulating layer and in direct contact with the isolation insulating layer.
 4. The semiconductor device of claim 3, wherein a thickness of the second metal layer is in a range from 0.5 nm to 3 nm.
 5. The semiconductor device of claim 3, wherein the second metal layer is in contact with the first silicide layer.
 6. The semiconductor device of claim 1, wherein the first metal element is at least one of Co, Ti, Ta, W and Ni.
 7. The semiconductor device of claim 1, wherein the second metal element is at least one of Co, Ti, Ta, W and Ni.
 8. The semiconductor device of claim 1, wherein the crystal semiconductor layer is doped with impurities at an amount of 2×10²⁰ cm⁻³ to 1×10²¹ cm³.
 9. The semiconductor device of claim 6, wherein the impurities are phosphorous.
 10. The semiconductor device of claim 1, wherein the first metal element has a lower silicide formation temperature than a second metal element.
 11. The semiconductor device of claim 1, wherein the crystal semiconductor layer is disposed on a top face and side faces of the upper layer of the fin structure of the source and fully covers the upper layer of the fin structure of the source.
 12. The semiconductor device of claim 10, wherein the first silicide layer is disposed on side faces of the crystal semiconductor and the second silicide layer is disposed on a top face of the crystal semiconductor.
 13. A semiconductor device comprising: a first fin structure and a second fin structure both disposed over a substrate, each of the first and second fin structures including an upper layer being exposed from an isolation insulating layer, wherein: each of the first and second fin structures includes a source region and a drain region, the upper layer of each of the first and second fin structures at each of the source region and the drain region is covered by a crystal semiconductor layer, the crystal semiconductor layer is covered by a first silicide layer formed by Si and a first metal element and a second silicide layer formed by Si and a second metal element different from the first metal element, and the second silicide layer covers a different portion of the crystal semiconductor layer than the first silicide layer.
 14. The semiconductor device of claim 13, wherein the first and second silicide layers are covered by a first metal layer containing the second metal element.
 15. The semiconductor device of claim 14, wherein the silicide layer disposed over the first fin structure is discontinuous from the silicide layer disposed over the second fin structure.
 16. The semiconductor device of claim 15, wherein a second metal layer made of the first metal element is disposed between the first metal layer and the isolation insulating layer and in direct contact with the isolation insulating layer.
 17. The semiconductor device of claim 16, wherein the second metal layer is disposed between the silicide layer disposed over the first fin structure and the silicide layer disposed over the second fin structure.
 18. A semiconductor device comprising: a first fin structure, a second fin structure and a third fin structure, all disposed over a substrate, each of the first to third fin structures including an upper layer being exposed from an isolation insulating layer, wherein: each of the first to third fin structures includes a source region and a drain region, the upper layer of each of the first to third fin structures at each of the source region and the drain region is covered by a crystal semiconductor layer, the crystal semiconductor layer is covered by a silicide layer, the silicide layer is covered by a first metal layer made of a first metal element, and a second metal layer made of a second metal element different from the first metal element is disposed between the first metal layer and the isolation insulating layer and between the source regions of first and the second fin structures.
 19. The semiconductor device of claim 18, wherein: the silicide layer includes a first silicide layer formed by Si and the first metal element and a second silicide layer formed by Si and the second metal element, and the second silicide layer covers a different portion of the crystal semiconductor layer than the first silicide layer.
 20. The semiconductor device of claim 19, wherein the first metal layer filly fills spaces between the source regions of first and the second fin structures and the source regions of second and the third fin structures. 